Radio link aggregation

ABSTRACT

It is provided a network entity (10) for grouping traffic in a communication network onto a defined connection comprising a plurality of output links (1 . . . L), wherein the traffic comprises a plurality of input streams (1 . . . S+1 . . . S+A), each input stream carrying symbol blocks. The network entity further comprises a scheduler (100) for associating, for all symbol blocks that are to be transmitted during a predetermined time interval, each of the symbol blocks to be transmitted with a corresponding output link according to a one to one correspondence. It is also provided a corresponding network entity for ungrouping traffic, corresponding system and method.

TECHNICAL FIELD

The present invention relates to communication in a network and moreparticularly to a network entity for grouping traffic onto a definedconnection, a network entity for ungrouping traffic in a communicationnetwork from a defined connection, a system for exchanging traffic in acommunication network over a defined connection and correspondingmethods.

BACKGROUND

The present invention relates to transmissions in a communicationnetwork and in particular it is concerned with multiplexing and bundlingtechniques for transmission in a communication network.

Traditional networks are designed for TDM services (for instanceSONET/SDH/PDH). These networks are typically designed for supportingpeak usage of bandwidth requirements and require a high reliability. TDMsystems must be designed with sufficient link margin to guaranteetransmission even under worst case condition like rain and fading.Furthermore SONET/SDH radio systems typically install redundant linksfor radio protection switching. Thus under normal circumstances TDMnetworks are under utilized and have spare capacity. Besides thetraditional transmission of TDM services there is an increasing demandfor the transmission of computer data (e.g. Ethernet/IP). These data is“bursty” and is transmitted in packets. Packet networks profit fromradio links which uses adaptive modulation to offer a higher bandwidthunder good environmental conditions.

There is a demand for support of faster interface ports, too. Examplesare Gigabit Ethernet for packet services or STM-4 for traditional TDMservices. However, traditional TDM radio links are not designed for suchhigh bandwidth. This is because of technical but also because ofregulative reasons. Technical reasons comprise limited resolution ofavailable ADCs (analog-digital-converters) and/or DAC(digital-analog-converters), complex design of highly selective analogwideband filters, desired system modularity (i.e. possibility to extendthe capacity later), trade-offs between modulation order and oscillatorphase noise sensibility, new technologies as digital amplifierlinearization which requires much higher sampling rate than thebandwidth of the user data, thermal problems, etc. . . Regulativereasons comprise fixed assignment of maximum transmission power andchannel bandwidth by regional regulation authorities.

Under the circumstances described above it is clear that it is often notpossible to transmit higher data rates over a single radio link. Linkbundling can be used to overcome this bottleneck. This allows thetransmission of GbE or STM-4.

It is known in the art parallel usage of TDM and packet services.Adaptive modulation and coding is also known. However, the knowntechniques suffer from a limited bandwidth capacity limited to thecapacity of the single therein described and suggested link.

Nowadays there exists radio system which bundles two or more synchronousradio channels to form an aggregated channel with a higher bandwidth(e.g. for transmission of a STM-4 channel over 2 or for 4 radiochannels). These SDH or SONET radio transmission systems generallyrequire a high reliability and use radio protection switching. However,the known mentioned implementation is not flexible and limited to veryspecial cases, namely transmission of ST-4 over 2 or more radio links.

There are also many systems documented which aggregate multiple links toform a service independent port with a higher bandwidth as each singlelink. With a TDM sub layer like SDH high rate packet services aretransmitted over an aggregation of virtual TDM links. ITU-T G.707 andITU-T G.783 discloses such an inverse multiplexing technique for SDHnetworks (see VCAT). The Link Capacity Adjustment Scheme (LCAS)specified in ITU-T G.7042 allows dynamically changing the bandwidth ofvirtual concatenated containers. A more flexible system is described inHari Adiseshu, Guru M. Parulkar and George Varghese: “A Reliable andScalable Striping Protocol”, Proceedings SIGCOMM 1996, pp. 131-141. Itis noted that these systems are initially designed for asynchronouslinks.

The mentioned prior art solutions suffer however from a series ofproblems and disadvantages as summarized above and in the following.

VCAT and LCAS described in ITU-T G.707/ITU-T G.783/ITU-T G.7042 aredesigned for SDH networks. These systems are not very effective (e.g.SDH overhead, resource requirements for handling of many VCG's members).Because of the SDH hierarchy these systems are designed for fixed linkbandwidth which limits the use of adaptive modulation and coding.

The bundling systems described in the paper of Adiseshu et al. aredesigned for asynchronous links. With an asynchronous aggregation systemit gets very complicated to handle adaptive modulation and coding.Although we may foresee solving this problem by packet transmission withsequence numbers, still such a solution would result in causing morelatency. In particular the transmission of low rate TDM services inpackets causes a high delay.

In summary, the prior art does not provide a resource efficient andflexible solution for aggregating data over a communication network.With reference to radio links, furthermore, there is no radio systemwhich makes an effective use of resources.

SUMMARY OF THE INVENTION

An object of the present invention is to provide improvements over knownprior art techniques of grouping or ungrouping traffic onto or from adefined connection comprising a plurality of links.

According to a first embodiment of the present invention, a networkentity is provided for grouping traffic in a communication network ontoa defined connection comprising a plurality of output links. The networkentity is a component of the communication network adapted for handlingtraffic. In one example the network entity is a network node or device.In other examples, the network entity may be distributed over severalnetwork nodes or devices or may be comprised within a network node ordevice. The network entity may be implemented in hardware, software orany suitable combinations thereof.

The traffic comprises all type of information that can be communicatedover the communication network. Examples of traffic are data, voice,signalling messages or overhead information associated to othertransmitted information like data or voice. The network entity issuitable for grouping the traffic arriving at the network entity andthat is supposed to be forwarded by the network entity. The networkentity is adapted to group the traffic onto a defined connectioncomprising a plurality of output links. Grouping traffic implies thatthe traffic, which is incoming the network entity, is recombined orrearranged when or before being output from the network entity. In otherwords, the same information or parts of the information received at thenetwork entity are output from the network entity in a recombined orrearranged form. The output links which form the defined connection areany kind of links suitable for carrying the recombined or rearrangedtraffic output from the network entity. The defined connection is anytype of connection, physical or logical, suitable for being establishedbetween the network entity and another network entity. In one example,the defined connection can be a point to point connection.

The mentioned traffic comprises a plurality of input streams whereineach input stream carries symbol blocks. An input stream is a successionover time of information comprised in the mentioned traffic. Forexample, it may be a succession of information related to data, voice,signalling or any other type of information exchanged within thenetwork. A stream may be associated to an input connection, physical orlogical, or to a set or group of input connections, physical or logical,wherein these input connections are input to the network entity.

A symbol block represents a predetermined unit of the informationcomprised in said traffic. A symbol block can for instance be a singlebit or a given number of bits. In another example a symbol block can bea word that, depending on the architecture chosen for implementing thesystem, may comprise 8, 16, 32, 64, etc. . . bits.

The network entity according to this embodiment of the invention furthercomprises a scheduler for associating, for all symbol blocks that are tobe transmitted during a predetermined time interval, each of the symbolblocks that are to be transmitted with a corresponding output linkaccording to a one to one correspondence. In other words, the schedulerassociates, during a predetermined time interval, each symbol block thatneeds to be transmitted during this predetermined time interval to anoutput link so that it can be forwarded onto the defined connection. Theassociation is made according to a one to one correspondence. Thepredetermined time interval indicates a known or predetermined durationin time. In one example, the predetermined time interval comprises theduration in time of a frame of a time division multiplexing protocol.The scheduler of the network entity can be implemented in hardware,software or any combination thereof as the skilled person would deemsuitable according to circumstances. The one to one correspondence usedby the scheduler for associating is a relationship that associates eachof the symbol blocks to be transmitted within the predetermined timeinterval to the output links such that each symbol block is associatedto one output link only. It is noted that more symbol blocks to betransmitted within the same time interval can be associated to the sameoutput link. Any kind of relationship is suitable for implementing theone to one correspondence as long as for each single symbol block to betransmitted there is only one output link associated. The one to onecorrespondence can be calculated within the network entity or may betransmitted to the network entity at predetermined time instants.Examples may be foreseen wherein the one to one correspondence is partlycalculated within the network entity and/or partly transmitted to thenetwork entity.

According to a second embodiment of the invention, it is provided anetwork entity for ungrouping traffic in a communication network from adefined connection comprising a plurality of input links onto aplurality of output streams. The network traffic of the secondembodiment relates to information in a communication network asexplained with reference to the traffic of the first embodiment.According to the second embodiment, the traffic comprised on a definedconnection, which can be either physical or logical, is grouped. In oneexample the grouping is performed by the network entity of the firstembodiment. However, it is noted that the network entity of the secondembodiment is not limited to such case but is arranged for functioningon any type of grouped traffic transmitted on a defined connection. Thenetwork entity of the second embodiment therefore ungroups ordisaggregates the traffic from the defined connection into a pluralityof output streams. For what concerns the input links and the outputstreams the same considerations made for the output links and inputstreams, correspondingly, of the first embodiment are as valid. Similarconsiderations as made with reference to the fist embodiment apply herefor the defined connection and the predetermined time interval. Thescheduler can be implemented in hardware, software or any suitablecombination thereof. When the network entity of the second embodiment isadapted to interwork with the network entity of the first embodiment, itis noted that preferably the number of input links of the network entityof the second embodiment is equal to the number of output links of thenetwork entity of the first embodiment. However, it is noted that theinvention is not restricted to this particular case since othersituations may be foreseen wherein between the network entity of thefirst embodiment and the network entity of the second embodiment furthernodes may be comprised, e.g. bridge devices. The input links of thesecond embodiment carry symbol blocks, wherein a symbol block is asdefined with reference to the first embodiment. The network entity ofthe second embodiment further comprises a scheduler for associating, forall the symbol blocks that are received during a predetermined timeinterval, each of the received symbol blocks with a corresponding outputstream according to a one to one correspondence. In other words, thescheduler of the second embodiment associates each of the symbol blockswhich are received during the predetermined time interval to an outputstream, such that for each of the received symbol blocks there is onlyone output stream. The one to one correspondence is a relationship whichensures that to each received symbol blocks there is only one outputstream to which said received symbol block is associated.

In the example wherein the network entities of the first and secondembodiments are arranged for interworking directly over the same definedconnection comprising a plurality of links, the one to onecorrespondence of the two network entities correspond to the samerelationship. Thus, the traffic from input streams of the first networkentity is grouped, forwarded to the second network entity wherein it isungrouped to output streams corresponding to the input streams of thefirst network entity.

However, the invention is not restricted to such a case. For instance,when between the entities of the first and second embodiments furtherentities are present—like for instance bridging devices—animplementation is foreseen wherein the one to one correspondences of thenetwork entities of the two embodiments correspond to two differentrelationships.

According to a third embodiment of the invention, it is provided asystem for exchanging traffic in a communication network over a definedconnection comprising a plurality of links. With reference to thetraffic, the defined connection and the plurality of links the sameconsiderations apply as made for, correspondingly, the communicationnetwork, the defined connection and the output links of the firstembodiment. The system comprises a first network entity for groupingtraffic onto the defined connection. The traffic comprises a pluralityof input streams, wherein each of the input streams carries symbolblocks. The first network entity further comprises a first scheduler.The first scheduler is adapted to associate, for all the symbol blocksthat are to be transmitted during a predetermined time interval, each ofthe symbol blocks that are to be transmitted with a corresponding linkaccording to a first one to one correspondence. In other words, the oneto one correspondence is a first relationship that ensured that for eachsingle block that is to be transmitted during a predetermined timeinterval there is only one associated link.

The system further comprises a second network entity for ungroupingtraffic in the communication network from the defined connectioncomprising the plurality of links onto a plurality of output streams,wherein the mentioned links carry symbol blocks. In other words, thesecond network entity is adapted for ungrouping the traffic which wasgrouped by the first network entity. The second network entity ungroupsthe traffic onto the plurality of output streams. The second networkentity further comprises a second scheduler for associating, for all thesymbol blocks that are received during the predetermined time interval,each of the received symbol blocks with a corresponding output streamaccording to a second one to one correspondence. In other words, thesecond scheduler of the second network entity is adapted to associateeach symbol block which is received in the predetermined time intervalto only one output stream. The second one to one correspondence is arelationship that ensures that every received symbol block is associatedto only one output stream.

According to a fourth embodiment of the invention, it is provided amethod for grouping traffic in a communication network onto a definedconnection comprising a plurality of output links. The traffic comprisesa plurality of input streams wherein each input stream carries symbolblocks. The method then foresees a step of associating, in a networkentity, for all the symbol blocks that are to be transmitted during apredetermined time interval, each of the symbol blocks that is to betransmitted with a corresponding output link according to a one to onecorrespondence. The same consideration made with reference to theprevious embodiments, are also valid for the method for grouping trafficembodying the invention.

According to a fifth embodiment of the present invention, it is provideda method for ungrouping traffic in a communication network from adefined connection comprising a plurality of input links onto aplurality of output streams, wherein each input link carries symbolblocks. The method according to the fifth embodiment comprises the stepof associating, in a network entity, for all the symbol blocks that arereceived during a predetermined time interval, each of the receivedsymbol blocks with a corresponding output stream according to a one toone correspondence. In other words, the method for ungrouping foresees astep of associating each received symbol block with a correspondingoutput stream. The one to one correspondence is responsible for ensuringthat each received symbol block is associated to only one output stream.

According to another embodiment of the present invention, it is provideda computer program product which comprises program parts. The programparts are arranged, when executed on a programmable processor, forconducting the method of grouping traffic according to the above fourthembodiment and/or the method of ungrouping traffic according to theabove fifth embodiment.

Furthermore, according to another embodiment of the present invention,it is provided a method which comprises the steps of the methodsaccording to the fourth and fifth embodiments of the present invention.

Further advantageous embodiments of the invention are provided in theindependent claims.

One of the advantages provided by the invention consists in a moreflexible and efficient usage of network resources for transmittingtraffic over a network.

Further advantages will become evident in conjunction with thedescription of the different examples embodying the invention.

Furthermore, the present invention obviates at least some of thedisadvantages of the prior art, as for instance above explained, andprovides improved network entities, a system and methods for exchangingtraffic in a communication network.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block functional diagram of a network entity for groupingtraffic according to an embodiment of the present invention;

FIG. 2 is a block functional diagram of a network entity for ungroupingtraffic according to another embodiment of the present invention;

FIG. 3 is a block functional diagram of a system for exchanging trafficin a communication network according to an embodiment of the presentinvention;

FIG. 4 is a schematic flow chart of a method for grouping traffic in acommunication network according to an embodiment of the presentinvention;

FIG. 5 is a block functional diagram of a method for ungrouping trafficin a communication network according to an embodiment of the presentinvention;

FIG. 6 is a block functional diagram of a basic architecture of afurther embodiment of the present invention;

FIG. 7 illustrates an example of link aggregation starting from havingthree links;

FIG. 8 is a block functional diagram illustrating a transmit schedulingarchitecture according to a further embodiment of the present invention;

FIG. 9 is a block functional diagram of a receiver schedulingarchitecture according to a further embodiment of the present invention;

FIG. 10 illustrates an example of a scheduling control table at thetransmitter and receiver side according to an embodiment of theinvention;

FIG. 11 illustrates an example of a scheduling control table withdifferent data width according to an embodiment of the invention;

FIG. 12 illustrates a scheduling control table generation according to afurther embodiment of the present invention;

FIGS. 13A and 13B are schematic flow charts showing an example ofgenerating a look up table according to further embodiments of thepresent invention.

FIG. 14A shows the Service MUX table produced according to the algorithmof FIGS. 13A and 13B when applied to a specific example;

FIG. 14B shows the Link MUX table produced according to the algorithm ofFIGS. 13A and 13B when applied to the same example referred in FIG. 14A;

FIG. 15A shows the optional adaptation in the transmitter when a nonsynchronous system is adapted to a synchronous implemented system;

FIG. 15B shows the corresponding adaptation in the receiver when a nonsynchronous system is adapted to a synchronous implemented system.

DETAILED DESCRIPTION

In the following, preferred embodiments of the invention will describedwith reference to the figures. It is noted that the followingdescription contains examples that serve to better understand theclaimed concepts, but should not be construed as limiting the claimedinvention.

FIG. 1 schematically illustrates a network entity for grouping trafficin a communication network. The traffic comprises all kind ofinformation that can be transmitted within a generic communicationnetwork. Examples of traffic are voice, data, signalling messages,overhead information accompanying voice or data, etc. . . . . Thedefined connection (150) indicates a generic connection, physical orlogical, over which the network entity forwards information like voice,data, signalling messages, etc. . . . . The connection (150) comprises aplurality of output links (1 . . . L). Grouping implies that the trafficis rearranged, for instance bundled or distributed, before or when beingsent out from the network entity.

The output links, representing any kind of physical or logical links towhich an output section of the network entity (10) is connected to, arecomprised in the connection (150) and are links suitable for carryingthe traffic grouped or rearranged by the network entity.

The traffic to be forwarded by the network entity comprises a pluralityof input streams (1 . . . S+1 . . . S+A), wherein each input streamcarries symbol blocks.

An input stream is a succession over time of information comprised inthe mentioned traffic. For example, it may be a succession ofinformation related to data, voice, signalling or any other type ofinformation exchanged within the network. A stream may be associated toan input connection, physical or logical, or to a set or group of inputconnections, physical or logical, wherein these input connections areinput to the network entity.

A symbol block represents a predetermined unit of the informationcomprised in said traffic. A symbol block can for instance be a singlebit or a given number of bits. In another example a symbol block can bea word that, depending on the architecture chosen for implementing thesystem, may comprise 8, 16, 32, 64, etc. . . bits.

The network entity comprises a scheduler (100). The scheduler (100) isarranged such that it associates each symbol block of the traffic to betransmitted, therefore received from one of the input streams (1 . . .S+1 . . . S+A), to one of the output links (1 . . . L). The scheduler isarranged to perform this association for all the symbol blocks that areto be transmitted during a predetermined time interval.

Furthermore, the scheduler performs the association according to a oneto one correspondence, which is a relationship that ensures that eachsymbol block incoming the network entity is associated to only oneoutput link going out from the network entity. A predetermined timeinterval indicates any time interval which has a finite length. In someexamples, as it will be explained in the following, the predeterminedtime interval corresponds to the duration in time of a frame in a timedivision multiplexing protocol. The scheduler can be implemented inhardware, software or any combination thereof as the skilled personwould deem suitable according to circumstances. In other words, thescheduler is adapted to perform the association for each symbol block.In one example, it repeats the step of associating according to the oneto one correspondence for each symbol block to be transmitted in thegiven time period.

The one to one correspondence can be calculated within the networkentity or may be transmitted to the network entity at predetermined timeinstants. Examples may be foreseen wherein the one to one correspondenceis partly calculated within the network entity and/or partly transmittedto the network entity. The advantage related to the transmission of theone to one correspondence to the network entity lies in that the networkentity results in a less complex entity and in that it can be easily andcentrally managed. It is noted that any kind of relationship is suitablefor implementing the one to one correspondence as long as for eachsingle symbol block to be transmitted there is only one output linkassociated.

According to a further embodiment of the invention, one or more of theoutput links and/or one or more of the input streams may have varyingcharacteristics. The characteristics are indicative of properties of theoutput links or input streams and may be expressed by parameters.Example of characteristics are the data rate, modulation schemes ormodulation parameters, average delay, average noise, typical signal tonoise ratio, etc. . . of a given input stream or a given output link.Some of theses properties or parameters may also be interrelated to eachother. For instance, the data rate may be directly linked to themodulation parameters chosen for the given stream or link. In otherwords, the characteristics comprise any kind of parameter that describesthe properties of a given link or a given stream. The links can be ofany kind, physical or logical, wired or wireless.

The characteristics of the input stream or output links may also referto parameters indicative of quality attributes of the streams or links.For instance, a characteristic may indicate whether an input stream ischaracterised by a constant data rate or by a non constant data rate. Ina further example, the characteristics may indicate whether a stream ora link is an idle stream or link, or whether it comprises padding symbolblocks. Characteristics may also express a parameter indicative of aqueue identifier of an input stream or output link; of a priority of oneof these queues; of a priority of one of the input streams or of one ofthe output links; of the level of reliability or of the level ofprotection of one of the input streams or of one of the output links,etc. . .

The characteristics may further vary over time due to a variety ofreasons. For instance, due to operation of the network or networkentities comprised in the network; as a consequence to a fault whichrenders one link or stream not available or which reduces the data rateand therefore the capacity of a given link or a given stream. Changingconditions of the transmission medium may also influence thecharacteristics of input streams or output links. For instance, theincrease of noise or the deterioration of the signal to noise ratio maytrigger an adaptation of the modulation parameters, which change to alower modulation scheme or add error correction (thus reducing availabledata rate) in order to compensate for the deteriorated conditions of themedium. As it is known, modulation parameters are typical of wired andwireless connections. In the case of output links being radio linkscharacterised by given modulation parameters, a problem that also oftenoccurs lies in that the modulation parameters have to be changeddepending on the condition of the medium. For instance, under adverseweather conditions, the attenuation on the medium increases and thesignal-to-noise ratio of the receiver decreases thus requiring amodification of the modulation parameters resulting in a decrease of thedata rate. Such situation is therefore reflected in the variation of thecharacteristic of the output link.

According to this further embodiment of the invention, the scheduler isfurther arranged to adapt to the varying characteristics. In otherwords, upon variation of the characteristics of at least one of theinput streams or one of the output links, the scheduler is configured toassociate each received symbol block to an output link according to aone to one correspondence that takes into account the variation of thecharacteristics. The scheduler, therefore, adaptively performs theassociation by changing the relationship as a consequence of thecharacteristics variation.

According to a further embodiment of the invention, the scheduler (100)of the network entity (10) is arranged to determine the one to onecorrespondence by means of an algorithm on the basis of algorithmparameters. In other words, the scheduler is arranged to perform analgorithm which produces the one to one correspondence. The produced oneto one correspondence can then be stored in a memory unit, not shown inFIG. 1, which may advantageously avoid the need to recalculate the oneto one correspondence. When needed, therefore, the scheduler maythereafter refer to the stored one to one correspondence and recalculatethe one to one correspondence only when at least one of thecharacteristics of the input streams and/or output links varies. In thefollowing parts of the description, see for instance the parts referringto FIG. 10, 11, 12 or 13, further embodiments will be providedillustrating examples of calculating the one to one correspondence. Theone to one correspondence, regardless of whether it is determinedthrough an algorithm or maintained or stored in a storing element of thenetwork entity, may be represented in a variety of forms. In oneexample, the one to one correspondence can be embodied in a table. Anexample of a suitable table would be a two columns table, wherein thefirst column comprises identifications, e.g. numbers, referring to thesymbol blocks received from the input streams and the second columnincludes identifications, e.g. numbers, referring to the output link towhich the symbol block of the input stream belonging to the same line ofthe table has been associated. The table may however have more columnsas explained for instance with reference to FIGS. 10 and 11 illustratingfurther embodiments of tables comprising the one to one correspondence.Furthermore, it is noted that the one to one correspondence does notnecessarily need to be represented through a table but may berepresented also by other means. For instance, any kind of database orlist of linked pointers may be used for representing the one to onecorrespondence. Further means may be foreseen by the skilled person, aslong as they are suitable for representing a relationship between eachreceived symbol block and one output link unambiguously associated tothe received symbol block.

As mentioned, the algorithm performed by the scheduler (100) in order todetermine the one to one correspondence is based on algorithmparameters. According to a further embodiment, the algorithm parametersmay comprise the varying characteristics of the output links (1 . . .L). Therefore, upon the variation of the characteristics of at least oneof the output links (1 . . . L), the algorithm parameters would alsochange. Consequently, the scheduler (100) would execute the samealgorithm according to the modified algorithm parameters thus producinga different one to one correspondence which is reflecting themodification of the characteristics of the output links. In one example,if one of the output links fail, e.g. due to a hardware failure of thetransmitting or receiving entity or due to a disruption of thetransmission medium over which said output link is carried on, thecharacteristics of that output link would vary thus indicating that forinstance the data rate of that output link has become zero. Thescheduler (100) would thus perform the calculation of a modified one toone correspondence which takes into account the new conditions on theoutput links. Another example consists in a modification of themodulation parameters of the output links, for instance in those caseswhere the output links are radio links having modulation parameters thatmay be changed. In an illustrative example, under adverse weatherconditions, the modulation parameters may be changed from for instance64 QAM to 8 QAM, in order to allow an error free reception which wouldnot be otherwise possible at higher data rates, i.e. with highermodulation schemes, due for instance to fading or rain which adverselyaffects the transmission conditions of the medium. Under thesecircumstances, the scheduler would calculate a modified one to onecorrespondence, which would consequently take into account the decreasedcapacity of the output links. Of course, also the opposite situation maybe foreseen. For instance, the one to one correspondence may berecalculated after reactivation of a link which had previously failed,upon improvement of the weather conditions allowing an increase of themodulation parameters, etc. . . .

It is noted that the algorithm parameters may also comprise varyingcharacteristics of an input stream. This means that the scheduler isconfigured to determine the one to one correspondence also uponvariation of characteristics of the input streams. Such situation couldoccur for instance when one of the input stream experiences a failure.The characteristics of that input stream would therefore indicate thatthe data rate corresponding to that stream suddenly becomes zero. Othersituations could of course be foreseen, for instance the addition of anew input stream due to the provision of new services; the change ordeterioration of requested data rates due to a change of the provisionof existing services; change of priority of one or more streams orqueues thereof as change in provisioning of services; etc. . . As aconsequence, therefore, the scheduler would adapt the one to onecorrespondence on the basis of the variation of the characteristics ofat least one of the input streams.

Evidently, the scheduler can also be configured in a further example foradapting the one to one correspondence also in response to asimultaneous variation of the characteristics of at least one inputstream and at least one output link.

Thanks to the scheduler, the network entity of the above embodiments isable to automatically respond to changing conditions on the output linksand input streams of the network entity. Thus, no intervention is neededby an operator or a network manager in order to adapt to the changedconditions. Since the scheduler performs the association on the basis ofsymbol blocks, the adaptation can furthermore be achieved in a reliableand flexible way. The advantage of the embodiments thus consist in avery efficient use of resources, thanks to the association made onsymbol block basis, and very flexible management of the same resources,thanks to the scheduler producing the adaptive one to onecorrespondence.

According to a further embodiment of the present invention, thealgorithm parameters may be received at the network entity, i.e. may besent to the network entity for instance by another network entity or bya network manager. This implies that the network entity does not need tobe necessarily capable of detecting a change in the conditions in orderto correspondingly modify the parameters needed for recalculating theone to one correspondence. The parameters corresponding to the change ofthe condition of the characteristics may be sent, in one example, byanother network device which is able to detect a fault and which timelyreports the changed parameter corresponding to the fault to thescheduler of the network entity. According to another example, a networkmanager or an operator may arrange for sending the parameters to thescheduler of the network entity, wherein the parameters reflect forinstance the change of configuration of the network, e.g. the additionof new links, the addition of new streams as consequence of the changeof provisioning of service, etc. . . Evidently, other examples may beforeseen as long as they provide the network entity with at least partof the one to one correspondence or with information allowing thescheduler to produce at least part of the one to one correspondence. Theadvantage of this embodiment relies in a more flexible operation of thenetwork entity, which is therefore adapted to timely and easily respondto any kind of situation. The parameters may be sent at regularintervals, for instance corresponding to programmed maintenance scheduleof the network, or may be sent upon a triggering condition. In oneexample, the triggering condition may be a detection of a fault or thedetection of a worsening in the condition of the medium as for instanceduring adverse weather conditions (e.g. fading or rain affecting awireless medium).

As mentioned, the network entity may further comprise a memory, notshown in FIG. 1, for storing the one to one correspondence. The one toone correspondence may be stored in a number of ways as the reader woulddirectly recognize. For instance, tables may be used having two, threeor four columns according to circumstances. FIGS. 10 and 11 showexamples of tables having three or four columns according to twoembodiments of the invention. It is noted that also a table having onlytwo columns would be enough, as explained earlier in this specification.Such a table may be derived from the one of FIG. 10 by removing thefirst column which reports a progressive number of the symbol blocks tobe transmitted during a predetermined time interval. However, the tableis only an illustrative way for storing the one to one correspondence.Other ways may be foreseen, for instance by use of a database, a list ofpointers, etc. . . as long said means allow storage or representation ofa correspondence between two types of information.

According to a further embodiment, a part of the stored one to onecorrespondence or the entirety of the one to one correspondence may betransmitted to the network entity prior to the storing. In one example,only a part of the table, or of the database or of the list representingthe one to one correspondence may be sent to the network entity, whichthereafter stores the received information in the memory.

In previous examples of the invention, it has been explained that thealgorithm parameters may be transmitted to the network entity such thatthe scheduler may calculate the one to one correspondence accordingly.However, according to another embodiment of the present invention, it isforeseen that the network entity receives the entire one to onecorrespondence without the need to perform any calculation. Suchconfiguration has the advantage of having a network entity characterizedby less complexity and therefore easier to implement. The calculation ofthe one to one correspondence may therefore be delegated to anothernetwork entity. The construction of the network entity would thereforebe easier and thus requiring less maintenance. Of course,implementations may be foreseen wherein only a part of the one to onecorrespondence table is sent to the network entity and not the entiretyof the one to one correspondence. According to the differentimplementations, this may be further implemented by sending only a partor the entirety of the table, the database or the list representing theone to one correspondence.

According to a further embodiment of the invention, the network entitymay further comprise a multiplexer for producing a service stream fromthe input streams. The network entity also comprises a de-multiplexerfor distributing the service stream to the output links, wherein themultiplexer and the de-multiplexer are adapted to be operated accordingto the one to one correspondence. According to this embodiment, thenetwork entity (10) comprises a multiplexer for creating a servicestream starting from the plurality of input streams. In other words, themultiplexer serializes the symbol blocks received from the plurality ofinput streams in one single stream herewith referred to as servicestream. The de-multiplexer comprised in the network entity (10) isoperated such that it distributes the symbol block serialized in theservice stream to the output links. In other words, the de-multiplexeroperates a distribution of serialized blocks to a plurality of outputlinks. The network entity operates the multiplexer and thede-multiplexer according to the one to one correspondence such that eachsymbol block received from the input stream is associated to only oneoutput link. The multiplexer and de-multiplexer may be in one exampleoperated under the control of the scheduler. A further example of thisimplementation will also be explained with reference to FIG. 8.

It should be noted, that the implementation of the network entity is notrestricted to the multiplexer and de-multiplexer described above. Infact, the distribution of received symbol blocks to the output links mayalso be realized by means of a second memory unit which is shared by aninput side of the network entity for receiving symbol blocks from theinput streams and an output side of the network entity sending symbolblocks to the output links. The received symbol blocks could be storedin said shared second memory, not illustrated in FIG. 1; the networkentity, for example by means of the scheduler, may be further arrangedsuch that a stored symbol block gets associated to an output link by thescheduler. Thereafter, the output link is adapted to read the associatedsymbol block from the shared second memory in order to transmit it outof the network entity over the associated output link.

Further variations may also be foreseen, whether the additional memoryrather than being shared by the input streams and output links isinstead to be found only on the input side, i.e. in relation to theinput streams, from which the symbol blocks are transferred to theoutput links after having been associated by the scheduler. One moreimplementation would foresee the usage of an additional memoryassociated with the output links, wherein the symbol blocks receivedfrom the input streams are stored after having been associated to anoutput link by the scheduler. Thereafter, the associated symbol blocksare transferred to the output links. As the reader will directlyrecognize, any suitable combination of the previously describedsolutions is suitable for carrying out the invention. Furthermore, thesecond or additional memory described above may be comprised in thepreviously described memory storing the one to one correspondence.

The usage of the association on a symbol block basis allows a veryefficient usage of the memory and thus results in a network entityhaving low memory requirements. The construction of the network entityresults therefore simple and inexpensive.

According to a further embodiment of the invention, the input streams (1. . . S+1 . . . S+A) may comprise at least one constant data rate inputstream (in FIG. 1, any of the illustrative links denoted as 1 . . . S)and at least one non-constant data rate input stream (in FIG. 1, any ofthe illustrative links denoted as S+1 . . . S+A). Constant data rateinput stream implies that the data rate is constant for at least acertain given amount of time, i.e. until there is a change in theprovisioning of the service or unless there is a fault in the network.Non-constant data rate are instead all those streams which do not have aconstant or predetermined data rate. Examples of non-constant data ratestreams are those characterized by a data rate which can suddenly varywithout prediction. Examples of non-constant data rate are bursty datatraffic; Ethernet traffic, etc. . . Another example of a non-constantdata rate is a stream which is idle. A further example is a streamcomprising padding information without carrying information associatedto services. The advantage of such embodiment consists in that thenetwork entity is adapted for grouping different kinds of input streams,therefore enhancing its flexibility.

The usefulness of introducing idle stream will also become apparent fromthe following example. Let us consider the case wherein one non constantdata rate input stream is intended to transmit data, for instanceEthernet data. When the stream has no data to transmit (e.g. thecorresponding FIFO is empty) idle data must be inserted at thetransmitter and removed at the receiver. The idle guarantees that theassociation of symbol blocks is still maintained also when there are nodata to be transmitted. The idle allows also rate adaptation.

It should be noted that the invention foresees the possibility of havingmore than one non constant data rate input stream. When this is thecase, the characteristics of the input streams may take into account theproportion of each non constant data rate input stream, for instance bymeans of weights parameters that can be input to the algorithm.

According to a further embodiment of the invention, the sum of symbolblocks of at least one non-constant data rate input stream (S+1) isadapted according to the difference between the sum of symbol blocks ofthe output links (1 . . . L) and the sum of symbol blocks of theconstant rate input streams (1 . . . S). In other words, the sum ofsymbol blocks of the non-constant data rate can be calculated as thedifference between the symbol blocks of the output links (1 . . . L),representing the capacity of the defined connection (150), and the sumof symbol blocks of the constant data rate input streams (1 . . . S),which are fixed, at least for a certain given period of time, since therate of those stream is constant. The advantage of this embodiment liesin that it is possible to efficiently and flexibly use the resource ofthe output links (1 . . . L) comprising the defined connection (150)depending on the conditions of the input streams and the conditions ofthe output links. For instance, when the sum of the data rates of theinput streams is lower than the capacity of the output links thedifference would represent available resources on the defined connection(150). These available resources on the defined connection, which may becalled also “spare capacity”, may be efficiently used by the nonconstant data rate streams. For instance, the available resources may beused for carrying best effort traffic (or Ethernet traffic, or genericdata traffic) up to the amount allowed by the “spare capacity”.Alternatively, the available resources may be filled with an idle streamwhich would then allow for rate adaptations between the input streamsand the output streams. According to a further alternative, theavailable resource or “spare capacity” could be used for providingprotection or redundancy.

The available resources of “spare capacity” may vary due to thevariation of the characteristics of the input streams or output links.The at least one non constant data rate stream (S+1 . . . S+A) wouldtherefore be automatically adapted according to the available resources.In the above example, therefore, the non-constant data rate input streamis adapting to the network conditions like faults, change of data ratesfor instance on the output links due to variation of the modulationparameters, etc. . . . . Evidently, the available resources on theoutput links may also be zero when the sum of symbol blocks of theconstant data rate streams is equal to the sum of symbol blocks of theoutput links.

Situations could also occur wherein the sum of symbol blocks on theoutput links is lower than the symbol blocks of the symbol blocks to betransmitted, for instance of the symbol blocks of constant data ratestreams. In such situations, the scheduler may be appropriatelyinstructed to use a modified one to one correspondence in order to adaptto said condition. For instance, by changing the characteristicsrelating to the priorities of at least an input stream, the one to onecorrespondence may be recalculated and as a consequence one of the inputstreams may be dropped.

According to a further embodiment of the invention, the network entityis suitable for operating when the input streams and/or the output linksare arranged in frames of a time division multiplexing protocol. In thiscase, the frame would have a duration corresponding to the predeterminedtime interval comprising the symbol blocks to be transmitted by thenetwork entity. Examples of time division multiplexing protocols arePDH, SONET/SDH, ISDN, as well as all other protocols which foresee theuse of a frame structure which repeats at regular intervals over time.In the following, for instance with reference to FIG. 6, 8 or 13,examples will be given of a network entity applied to a networkimplementing a time division multiplexing protocol.

In a further embodiment of the invention, the network entity describedabove comprises a point-point radio transmitter and/or a point-pointradio receiver. In this embodiment, the network entity is thereforeadapted to perform a point-point radio communication with anothernetwork entity adapted to interoperate with the network entity then ofFIG. 1.

According to the above embodiments, therefore, it can be obtained asystem which uses link bundling with word-by-word scheduling andadaptive modulation simultaneously. The system may be in furtherembodiments a radio system.

Reference will now be made to FIG. 2, showing an illustrative blockdiagram of a network entity (20) for ungrouping traffic in acommunication network. The network entity (20) is adapted for ungroupingtraffic in a communication network from a defined connection comprisinga plurality of input links (1 . . . L′) onto a plurality of outputstreams (1 . . . S′+1 . . . S′+A′), wherein for the network traffic thesame considerations apply as made above. In one example the grouping isperformed by the network entity (10) described with reference to FIG. 1.However, it is noted that the network entity (20) is not limited to suchcase but is arranged for functioning on any type of grouped traffictransmitted on a defined connection. The network entity (20) forungrouping traffic is therefore adapted to ungroup or disaggregate thetraffic from the defined connection into a plurality of output streams(1 . . . S′+1 . . . S′+A′). For what concerns the input links and theoutput streams the same considerations apply as made for the outputlinks and input streams, correspondingly, with reference to the networkentity for grouping traffic of FIG. 1. Similar considerations as madeearlier with reference to FIG. 1, apply here for the defined connection,the predetermined time interval and the symbol blocks.

The network entity (20) further comprises a scheduler (200) forassociating, for all the symbol blocks that are received during apredetermined time interval, each of the received symbol blocks with acorresponding output stream (1 . . . S′+1 . . . S′+A′) according to aone to one correspondence. In other words, the scheduler of the secondembodiment associates each of the symbol blocks which are receivedduring the predetermined time interval to an output stream (1 . . . S′+1. . . S′+A′), such that for each of the received symbol blocks there isonly one output stream (1 . . . S′+1 . . . S′+A′). The one to onecorrespondence is a relationship which ensures that to each receivedsymbol blocks there is only one output stream to which said receivedsymbol block is associated. In other words, the scheduler is adapted toperform the association for each symbol block. In one example, itrepeats the step of associating according to the one to onecorrespondence for each symbol block to be transmitted in the given timeperiod.

The scheduler (200) can be implemented in hardware, software or anysuitable combination thereof. In one example, the network entity (20) isadapted to interwork with the network entity (10) of FIG. 1: in thiscase the number of input links of the network entity (20) is preferablyequal to the number of output links of the network entity (10). However,it is noted that the invention is not restricted to this particularexample. Other situations may be foreseen wherein between the networkentity (10) and the network entity (20) further nodes are comprised,e.g. bridge devices. The input links (1 . . . L′) carry symbol blocks,wherein a symbol block is as defined previously.

Further modification of the network entity (20) depicted in FIG. 2 canbe made as described with reference to the network entity (10) ofFIG. 1. For instance, also the network entity (20) may be adapted suchthat the scheduler (200) is arranged for adapting to varyingcharacteristics of the input links and/or output streams. Furthermore,the scheduler (200) may be arranged to calculate the one to onecorrespondence according to an algorithm based on algorithm parameters.The algorithm and parameters thereof may be the same as the onesimplemented in network entity (10) or may be different and distinct in amodified embodiment, as long as said algorithm and algorithm parametersare suitable for producing the one to one correspondence for networkentity (20). In a further embodiment, the algorithm parameters maycomprise varying characteristics of at least one of the input links andoutput streams. The algorithm parameters or the one to onecorrespondence may be received at the network entity (20) as describedwith reference to the network entity (10) of FIG. 1. Furthermore,similar consideration apply to the network entity (20) as made fornetwork entity (10) with reference to the constant data rate streams andnon constant data rate streams, to the adaptation of the one to onecorrespondence according to the difference between the sum of symbolblocks of the input links and sum of symbol blocks of output streams.The one to one correspondence of network entity (20) can be representedin the same ways as described for network entity (10). For instance as atable, database, list, etc. . . The network entity may be furtherrealized by means of a de-multiplexer and multiplexer. A detailedexample will be given with reference to FIG. 9. Evidently, differentimplementations using a second or additional memory are possible asdescribed with reference to the network entity (10) of FIG. 1. Insummary, it is possible to put into practice variations and furtherembodiments of the network entity (20) corresponding to those made forthe network entity (10) of FIG. 1.

In the example wherein the network entities (10) and (20) are arrangedfor interworking directly over the same defined connection (150)comprising a plurality of links, the one to one correspondence of thetwo network entities (10) and (20) correspond to the same relationship.Thus, the traffic from input streams (1 . . . S+1 . . . S+A) of thefirst network entity is grouped, forwarded to the second network entitywherein it is ungrouped to output streams (1 . . . S′+1 . . . S′+A′)corresponding to the input streams of the first network entity. In suchan example S would be equal to S′ and A to A′.

However, the invention is not restricted to such a case. For instance,when further entities (e.g. bridging devices) are present between thenetwork entities (10) and (20), an implementation is foreseen whereinthe one to one correspondences of the network entity (10) is differentfrom the one to one correspondences of the network entity (20).

The network entity (10) and (20) may also be implemented in the samenetwork entity, which would comprise a first part including the networkentity (10) and a second part including the network entity (20). Suchnetwork entity would therefore be adapted to group and forward thegrouped traffic over the connection (150) by means of the first part. Atthe same time, such network entity would be also suitable to ungroup andforward the ungrouped traffic received from the connection (150) bymeans of the second part. The two parts may implement different anddistinct one to one correspondence, one valid for grouping traffic to beforwarded and one valid for ungrouping the received traffic. Suchimplementation would allow an asymmetric configuration of the definedconnection (150, 250, 350). In another example, the two parts wouldimplement the same one to one correspondence. Such configuration wouldresult in a less complex construction and implementation of the networkentity.

Reference will now be made to FIG. 3, wherein it is depicted anillustrative system according to another embodiment of the invention.The system of FIG. 3 is adapted to exchange traffic in a communicationnetwork over a defined connection (350) comprising a plurality of links.The links may be in certain examples the same as the output links (1 . .. L) of FIG. 1 or the links (1 . . . L′) of FIG. 2. The connection (350)may be in some examples the same connection (150) of FIG. 1 or the sameconnection (250) of FIG. 2. Similar considerations as made above withreference to the traffic, symbol blocks, links and streams apply also tothe system of FIG. 3.

The system comprises a first network entity (10) for grouping trafficonto the defined connection (350). The traffic comprises a plurality ofinput streams (1 . . . S+1 . . . S+A), wherein each of the input streamscarries symbol blocks. The first network entity further comprises afirst scheduler (3100). The first scheduler (3100) is adapted toassociate, for all the symbol blocks that are to be transmitted during apredetermined time interval, each of the symbol blocks that are to betransmitted with a corresponding link according to a first one to onecorrespondence. In other words, the one to one correspondence is a firstrelationship that ensures that for each single block that is to betransmitted during a predetermined time interval there is only oneassociated link.

The system further comprises a second network entity (320) forungrouping traffic in the communication network from the definedconnection (350) comprising the plurality of links onto a plurality ofoutput streams (1 . . . S′+1 . . . S′+A′), wherein the mentioned linkscarry symbol blocks. In other words, the second network entity isadapted for ungrouping the traffic which was grouped by the firstnetwork entity. The second network entity ungroups the traffic onto theplurality of output streams. The second network entity further comprisesa second scheduler (3200) for associating, for all the symbol blocksthat are received during the predetermined time interval, each of thereceived symbol blocks with a corresponding output stream according to asecond one to one correspondence. In other words, the second scheduler(3200) of the second network entity (320) is adapted to associate eachsymbol block which is received in the predetermined time interval toonly one output stream. The second one to one correspondence is arelationship that ensures that every received symbol block is associatedto only one output stream.

In one illustrative implementation of the system of FIG. 3, the firstnetwork entity and the second network entity may be arranged tointerwork. In such a case, the second one to one correspondence of thesecond network entity (320) is such that the output streams of thesecond network entity (320) correspond to the input streams of the firstnetwork entity (310). In other words, according to this implementationthe first and second one to one correspondences represent the samerelationship. According to the specific implementation of the one to onecorrespondence, in some examples of this implementation the first andsecond one to one correspondences may be the same, e.g. the table may bethe same in the first and second network entities (when the table ischosen for representing the one to one correspondence).

According to another illustrative implementation of the system of FIG.3, the first and second network entities are inter-related entities thatdo not communicate directly but through intermediate entities or deviceslike bridge devices. In said circumstances, the first and second one toone correspondences are not necessarily the same since the relationshipsthey define depend on the intermediate devices operating between thefirst and the second network entity.

Reference will now be made to FIG. 4, illustrating a flow chartaccording to a method embodying the invention. The method illustrated bythe flow chart of FIG. 4 is for grouping traffic in a communicationnetwork onto a defined connection comprising a plurality of outputlinks. The method is suitable, for instance, for operating a networkentity as described with reference to FIG. 1. The method then foresees astep (400) of associating, in a network entity, for all the symbolblocks that are to be transmitted during a predetermined time interval,each of the symbol blocks that is to be transmitted with a correspondingoutput link according to a one to one correspondence. In Step 410 themethod may preferably perform a further step of storing the result, orof waiting for a trigger condition in order to repeat step 400, orreceiving a one to one correspondence from another network entity, etc.. . The method of FIG. 4 is however not restricted to the implementationin network entity (10). In fact, it may also completely or partially beperformed in another network entity and the produced associationresulting in a one to one correspondence may then be transferred to thenetwork entity (10). For instance, a variation of the method may foreseethe calculation of the one to one correspondence in one network entityand the transmission of the calculated one to one correspondence to thenetwork entity (10) which perform the grouping accordingly.

Reference will now be made to FIG. 5, illustrating a flow chartaccording to a further method embodying the invention. Accordingly, itis provided a method for ungrouping traffic in a communication networkfrom a defined connection comprising a plurality of input links onto aplurality of output streams, wherein each input link carries symbolblocks. The method is suitable, for instance, for operating a networkentity (20) as described with reference to FIG. 2. The method of FIG. 5comprises the step of associating, in a network entity, for all thesymbol blocks that are received during a predetermined time interval,each of the received symbol blocks with a corresponding output streamaccording to a one to one correspondence. In other words, the method forungrouping foresees a step of associating each received symbol blockwith a corresponding output stream. The one to one correspondence isresponsible for ensuring that each received symbol block is associatedto only one output stream. The method of FIG. 5 is however notrestricted to the implementation in network entity (20). In fact, it mayalso completely or partially be performed in another network entity andthe produced association resulting in a one to one correspondence maythen be transferred to the network entity (20). For instance, avariation of the method may foresee the calculation of the one to onecorrespondence in one network entity and the transmission of thecalculated one to one correspondence to the network entity (20) whichperform the ungrouping accordingly.

According to another embodiment of the present invention, it is provideda computer program product which comprises program parts. The programparts are arranged, when executed on a programmable processor, forconducting the method of grouping traffic as described with reference toFIG. 4 and/or the method of ungrouping traffic as described withreference to FIG. 5.

Furthermore, it is possible to combine together the methods of FIGS. 4and 5.

Reference will now be made to further illustrative and non limitingexamples to which the present invention can be applied.

One example is now provided relating to radio transmissions and inparticular to a multiplex and bundling technique for transmission ofheterogeneous services over an aggregate of multiple point-to-pointradio links with adaptive (variable) transmission rates.

The provided example aggregates multiple radio links of variable datarates to form a service independent port with a higher bandwidth as eachsingle link. The radio links are synchronous to a common clock andimplement a radio frame (header section and payload section). In theprovided example, all radio frames have a common duration and arephase-aligned. Due to adaptive modulation the length of the payloadsection can vary.

All links together form a service stream which is also framed,synchronous and phase-aligned. Due to adaptive modulation and linkprotection the data rate of this service stream is variable. Synchronousdata services may be synchronized by data rate adaptation (e.g. STM-1,E1/T1, Ethernet) can be added and dropped to this framed service stream.

One service can be used for a packet interface with a variable data rate(e.g. Etherner, IP). A packet service may require packet additionalencapsulation or idle insertion. This could be implemented similar toGFP, LAPS or PPP. All other services have a fixed rate (e.g. STM-1,E1/T1).

Reference will now be made to FIG. 6, showing a basic architecture of anexample to which the invention can be applied. The presented examplerelates to a synchronous transmission system for heterogeneous servicesover multiple point-to-point links with variable transmission rates. Thelinks are bundled for increasing bandwidth and reducing latency. Inparticular the links can be radio channels which use adaptive modulationto adapt the transmission rate to varying environmental conditions suchas rain or fading.

The links are synchronous to a common clock and have a frame with headerand payload section. All frames are phase aligned and have a commonduration but the bit length of payload section can vary e.g. due toadaptive modulation. All links together form a framed service streamwith a higher bandwidth. Data services (e.g. STM-1, E1/T1, Ethernet) canbe added and dropped to this framed service stream.

The connection denoted with reference sign (650) is one example of theconnection (150) of FIG. 1, or (250) of FIG. 2 or (350) of FIG. 3.References 610, 625, 630 and 635 are examples of components comprised ina network entity (10) of FIG. 1. The streams (620) represent the inputstream, the links 640 are an example of the links (1 . . . L) output bythe network entity (10). In the example of FIG. 6, the links (640) arecombined by the combiner (645) in order to be carried on the connection(650). It is noted that this is not an essential feature but only apreferred one according to this example. The service switch (625) andlink switch (635) are responsible for distributing the symbol blocksfrom the input streams (620) to the output links (640). The serviceswitch (625) and link switch (635) operate under control of the transmitswitch algorithm (610), which is responsible for operating the switches(625) and (635) such that the one to one correspondence is respected.Reference (630) represents the service stream in the presented example.

Components (660, 675, 680, 685) may be comprised in a network entity(20) as depicted in FIG. 2. The streams (690) are an example of theoutput streams (1 . . . S′+1 . . . S′+A), the links (670) are an exampleof the links (1 . . . L′) input in the network entity (20). In theexample of FIG. 6, the links (650) are combined and distributed to links(670) by means of combiner (665). It is noted that this is not anessential feature but only a preferred one according to this example.The service switch (685) and link switch (675) are responsible fordistributing the symbol blocks from the input links (670) to the outputstreams (690). The service switch (685) and link switch (675) operateunder control of the transmit switch algorithm (660), which isresponsible for operating the switches (675) and (685) such that the oneto one correspondence is respected. Reference (680) represents theservice stream in the presented example.

Reference will now be made to FIG. 7 showing an example for the timevarying data rates with 3 links. The 3 links of FIG. 7 can be arepresentation of the links outgoing the network entity (10). The datarates of link 1 and link 2 change over time. The total capacity of theaggregation of the three links is shown in the bottom of the figure. Thetotal capacity is smoother than the capacity of the individual links.Therefore, by grouping links the resources can be more efficiently usedand the capacity of the grouped link is smoother.

Reference will now be made to FIG. 8, showing one illustrative basicscheduling architecture of the transmitting side. The architecture ofFIG. 8 is one example of the network entity illustrated with referenceto FIG. 1. It is noted that this is illustrative only and nonrestrictive for the invention. As explained previously, in fact, otherrealizations are also possible.

The architecture of FIG. 8 comprises a Transmission Service Multiplexer(Tx Service MUX 800), a Transmission Link Demultiplexer (Tx Link DEMUX850), a Calculated Look Up Table (Calculated LUT 820), a counter (822),a clock (824), ingress services (810), Link Control Data (852, 854,856), Common Control Data (858), Radio Transmitters with adaptive FECand modulation (862, 864, 866) and synchronous links with variable rates(870). It is noted that the ingress services (810) and the synchronouslinks with variable rates (870) are preferably synchronous.

However, also non synchronous streams or links may be adapted. Ways toachieve the adaptation will be explained later.

The TX Service MUX (800) and the Link DEMUX (850) are controlled by acommon Look-Up-Table (LUT 820). The MUX (800) and DEMUX (850) areresponsible for grouping the traffic according to the one to onecorrespondence stored in table (820). The first column of table (820) isonly the row index and is not strictly necessary. The second column ofthe LUT controls the TX Service MUX (800). The third column controls theTX Link DEMUX (850). Besides the transmitter inserts control data.Critical data is transmitted as common control data. It requiresefficient transmission error protection and is simultaneously sent onall links. Examples for common control data are service properties (e.g.priority, data rate, queue identifier) and link states (e.g. aggregationdata rate which depends on the link's PhyMode). The link control data isnot so sensitive to single transmission errors. Parameters concernsATPC, radio field identifier and polarization identifier (for XPIC). Aradio frame preamble is inserted before each frame, too.

FIG. 9 shows the corresponding scheduling architecture of the receiver.The architecture of FIG. 9 represents an example of the network entity(20) illustrated with reference to FIG. 2. The data flow is in theinverse as depicted in FIG. 8.

The architecture depicted in FIG. 9 comprises a Receiver ServiceDemultiplexer (RX Service DEMUX 900), a Receiver Link Multiplexer (RXLink MUX 950), egress services (910), a calculated Look Up Table(Calculated LUT 920), a counter (922), a clock (924), common controldata (958), Link control Data (952, 954, 956), radio receivers withadaptive FEC and modulation (960, 962, 964), links with variable rates(970). It is noted that the egress services (910) and the synchronouslinks with variable rates (970) are preferably synchronous.

In one example, the data within the network entity corresponding inputstreams and input links and the scheduler are synchronous to a commonclock. When the data incoming from the input streams is not synchronousto the common clock, then an adaptation may be performed. Thisadaptation of non synchronous stream to the internal clock is anoptional implementation that will be described later.

At the first stage the preamble is used for frame synchronization andthe control data is extracted. Then the frame data is forwarded to thelink and service scheduler which uses an identical LUT (920) as thetransmitter. The third column of the LUT controls the RX LINK MUX (900).The second column controls the RX Service DEMUX (950).

FIG. 10 shows an example for a scheduling control table (LUT). Generallyboth directions of a link are independent. So the LUTs for transmit andreceive direction can differ. This allows a very flexible realization.The LUT stores in this example the one to one correspondence of theinvention.

The entries of the LUT are calculated by an adaptation algorithm whichuses the same input parameters on both sides of the aggregation. Theresult of the adaptation algorithm must be unique. The table can bestored in memory or calculated in each frame once again.

FIG. 12 shows an example of how the Look Up Table (LUT) entries for thescheduling control table can be generated. Constant rate models are usedfor the emulation of the service and link rate. On the left side,reference 1000 indicated constant rate models for services, whilereference 1020 on the right hand side refers to constant rate models forlinks. Blocks S-1, . . . , S-M, S-I refer to service generation 1, M andIdle generation, correspondingly. Reference 1100 indicates anillustrative block for generating ServId-LinkId Pair, i.e. it is anexample of generating the one to one correspondence. 1030 refers to awrite pointer in the LUT. Blocks L-1 . . . L-L indicated link generation1 . . . L, correspondingly.

If one of the service models generates a word, this word is scheduled bya strict priority scheduler. The word is an example of the symbol blocksas intended in the present invention. Another scheduler processes thewords which are generated by the link models. The results of bothschedulers are combined to form a service-link pair which is stored inthe scheduling control table.

An algorithm based on counters is summarized in the following. It isnoted that the below algorithm is only an example. In fact, otheralgorithms would be suitable as long as they produce the one to onecorrespondence as presented previously. According to the presentillustrative algorithm, the service rate can be modelled by counters.The links rate can be modelled in a similar way. The main steps of thealgorithm can be summarized as in the following.

DEFINITIONS

-   M+1: number of services (M+1: idle, best effort, etc.)-   LwCBRk: number of words of service k per frame-   LwSFP: total number of words for aggregation=sum over LwCBRk,    1≤k≤(M+1)    Initialization at Frame Start:    -   ∀k: cbrk=LwCBRk, k=1 . . . M+1        Scheduling Until Frame End    -   ∀k: Service-generation, k=1 . . . M+1    -   while not all service FIFOs empty:        -   strict priority scheduling (read from FIFO)            Service-k Generation:    -   cbrk=cbrk+LwCBRk    -   if (cbrk≥LwSFP):        -   generate Cbr-k word (write to FIFO)        -   cbrk=cbrk−LwSFP            Input Parameters for the Algorithm are:    -   the TDM services with data rate (TDM), queue identifier and        priority,    -   the Ethernet service with queue identifier and priority,    -   the current data capacity of all links. Typically only a limited        set of different link data rates is used These are defined by a        PHYMODE set (modulation+FEC parameters)        Optional Parameters are:    -   Ethernet minimum data rate.

Thanks to the association made on a symbol block basis, a highefficiency and flexibility can be achieved. This also results in asimple and straightforward implementation of the transmitter andreceiver which do not need any complicated structure or architecture fordistributing the traffic thanks to the association on a symbol blocksbasis.

There can be further constraints for the scheduling algorithms: e.g. donot distribute a TDM services over multiple links. This can increase theavailability for the case that a link suddenly fails (e.g. hardwarefailure). Under normal circumstances (link is slowly degrading) this ishandled by the radio link control (change of adaptive modulation mode).Parameters indicating for instance a slow degradation are examples ofthe characteristics already introduced in the present invention.

The scheduling algorithm for the LUTs can also use several aggregationgroups with different qualities of service. For example there can be agood group (links with very low error ratio), a medium group (links withlow to medium error ratio) and a bad group (lost links or links withhigh error ratio). All this parameters are examples of the algorithmparameters as previously introduced.

In a preferred embodiment, the present system works fully synchronous toa common clock in each direction. But this is not a limitation for theinvention. In fact, asynchronous services and asynchronous channels canbe made synchronous with known methods like justification (e.g. bitstuffing like PDH) or pointer processing (e.g. see pointers inSDH/SONET). Thus, the present invention is suitable also forimplementation with non synchronous systems. Further details aboutadaptation of non synchronous systems will be later referred.

According to this example, the bundling technique uses adaptive LUTs(Look-Up-Tables) which allows a very flexible and fast realization. Thelink and service scheduler can work word-by-word where a word can be 8bit, 16 bit or 32 bit or something else. A larger word width allows afaster scheduling speed. All these are examples of possible choices forthe symbol blocks of the present invention.

For greater efficiency (less padding) at high data rates also mixedimplementations are possible. FIG. 11 shows a modified LUT for such anexample. The LUT has a fourth column for the data width. The generalscheduling width in this example is 16 bit. But some data is schedulingwith 8 bit only.

The service and link aggregation is controlled by a control plane. Forthis purpose additional control data is exchanged between thetransmitter and receiver. Some control data (like trigger for PhyMode orservice changes, enabling or disabling links from the aggregation)require synchronized actions at transmitter and receiver. Therefore thisdata requires a strong protection. This can be achieved by a combinationof the following mechanism:

-   -   repetition    -   checksum    -   transmission over multiple links

Some other parameters (like new service properties) must not getimmediately effective and can be handled by a protocol handshake (e.g.request and acknowledge).

Table 1 below shows the properties of the main control data.

Transmitter Receiver action reaction sphere of speed speed errorParameters action (master) (slave) sensitivity protection mechanismpreamble, link static — uncritical — radio field identifier,polarisation identifier ATPC link medium medium low checksum change ofPhyMode, link high high high repetition, checksum, disable/enable linkmultiple links from aggregation service changes aggregation low no highprotocol handshake, (not effective until checksum, multiple trigger)links trigger for service aggregation low high high repetition,checksum, changes (effective multiple links date) addition/removal oflink/ low low high protocol handshake, Links (unused by aggregationchecksum, multiple aggregation) links

FIGS. 13A and 13B provide further flow charts illustrating an example ofgenerating a look up table according to further embodiments of thepresent invention. Also this embodiment is based on counter. However, itis noted that any algorithm is suitable as long as it produces a one toone correspondence. In the following it is presented an example to whichthe algorithm shown in FIGS. 13A and 13B is applied. In the followingexample, denoted as Example A, low rates are chosen for explanationpurposes only.

Example A (Low Rates Only for Explanation):

-   frame duration=1 ms-   byte scheduling    3 Links:-   Link payload rate A: 2 kbits/s-   Link payload rate B: 5 kbits/s-   Link payload rate C 1 kbits/s-   Aggregation Payload rate: 8 kbits/s    2 Services:-   Service rate A: 6 kbits/s-   Service rate B: 2 kbits/s (e.g. Idle)

When applying the above example A to the algorithm of FIGS. 13A and 13B,the following results are produced as summarized in the below table.

Example A (Result): Service-Link-Mux Table Index ServiceId LinkId 1 1 22 1 1 3 1 2 4 2 2 5 1 2 6 1 1 7 1 2 8 2 3

FIG. 14A shows the Service MUX table produced according to the algorithmof FIGS. 13A and 13B when applied to the example A illustrated above.

In particular, FIG. 14A illustrates steps for generating the Service-MUXtable for Example A, with the following initialisation parameters.

Initialisation:

-   M:=2; LwSFP:=8;-   LwCBR(1):=6; LwCBR(2):=2;-   cbr(1):=6; cbr(2):=2;-   I:=1; K:=1.

FIG. 14B shows the Link MUX table produced according to the algorithm ofFIGS. 13A and 13B when applied to the example A illustrated above.

In particular, FIG. 14B illustrates steps for generating the Link-MUXtable for Example A, with the following initialisation parameters.

Initialisation:

-   N:=3; LwLkSFP:=8;-   LwLkSF(1):=2; LwLkSF(2):=5; LwLkSF(3):=1;-   lsf(1):=2; lsf(2):=5; lsf(3):=1;-   I:=1; K:=1.

As mentioned earlier in the description, the present invention may alsobe applied to non synchronous systems. In the following, it will beillustrated an adaptation between external interfaces and internalinterfaces for adapting non synchronous systems.

The assumption is made that in one example of the invention, theinternal interfaces are synchronous to a common clock (inclusive frameand phase). In the following, it will be explained how a non synchronoussystem can be applied to a synchronous implemented system.

If the input streams are not synchronous an adaptation function isrequired:

-   -   For constant data rate but asynchronous input streams the        adaptation can be done by known techniques as justification/bit        stuffing (see asynchronous multiplexing e.g. ITU-G.742).    -   For non constant data rate input streams (e.g. Ethernet or other        packet services) the rate adaptation can be done by idle        insertion (constant internal interface rate is faster than        current non constant external interface mean rate) or packet        discard (constant internal interface rate is slower than current        non constant external interface mean rate).

The external interfaces of the output links can be designed assynchronous interfaces with frames phase-aligned to the schedulingframe. In this case adaptation is not required for the link and featureslike adaptive modulation and coding are easier to handle. If someexternal link interfaces are not synchronous and phase-aligned, thenadaptation techniques like stuffing are also required.

FIG. 15A shows the optional service stream adaptation in thetransmitter. In the non limiting example, it is assumed here that thelink interfaces are synchronous and do not need adaptation.

FIG. 15B shows the corresponding adaptation in the receiver.

The present invention provides several advantages. The following is onlya list of some of the advantage:

-   -   full flexible multi service interface and multi air interface,    -   low latency (through byte-by-byte or word-by-word scheduling),    -   service prioritization (if not enough capacity available, low        priority services fails first),    -   high bandwidth efficiency (through adaptive modulation & FEC),    -   service reliability (parallel (redundant) transmission of vital        control data and link supervision),    -   efficient and fast implementation (with LUTs).

The skilled reader would however recognize that further advantages areprovided as explained in the present invention or as evident to theskilled reader.

Abbreviations used:

-   ADM Add/Drop Multiplexer-   ANSI American National Standards Institute-   ATM Asynchronous Transfer Mode-   ATPC Automatic Transmit Power Control-   ETSI European Telecommunication Standards Institute-   GbE Gigabit Ethernet-   GFP Generic Framing Procedure-   IP Internet Protocol-   ISDN Integrated Services Digital Network-   ITU International Telecommunications Union-   LAPS Link Access Procedure—SDH-   LCAS Link Capacity Adjustment Scheme-   LUT Look-Up-Table-   PhyMode Physical mode used by adaptive modulation-   PDH Plesiochronous Digital Hierarchy-   PPP Point-to-Point Protocol-   SDH Synchronous Digital Hierarchy-   SONET Synchronous Optical Network-   TDM Time Domain Multiplexing-   VCAT Virtual Concatenation-   VCG Virtual Concatenation Group-   VoIP Voice over IP-   XPIC Cross Polarization Interference Cancellation

The invention claimed is:
 1. A method, implemented in a network device,comprising: receiving a plurality of symbol blocks via a plurality ofinput streams, the plurality of symbol blocks to be transmitted within apredefined time period over a plurality of output links comprised in adefined connection; serializing the plurality of symbol blocks receivedvia the plurality of input streams into a service stream, and inresponse, scheduling transmission of each of the plurality of symbolblocks on one of the plurality of output links, the scheduling of thetransmission comprising distributing the symbol blocks from the servicestream to the plurality of output links according to a mapping of symbolblocks to output links; responsive to an input stream of the pluralityof input streams being empty, scheduling idle data for transmission overat least one of the plurality of output links such that the mapping ofsymbol blocks to output links is maintained; transmitting over thedefined connection via the plurality of output links according to thescheduling of the plurality of symbol blocks and the idle data.
 2. Themethod of claim 1, wherein scheduling the idle data for transmissioncomprises scheduling the idle data to fully utilize transmissioncapacity of the plurality of output links that will not be consumed bythe transmitting of the plurality of symbol blocks.
 3. The method ofclaim 1, wherein the scheduling transmission of each of the plurality ofsymbol blocks comprises scheduling transmission of at least one of theplurality of symbol blocks according to an instruction from a remotemanagement node.
 4. The method of claim 1, wherein the plurality ofinput streams, the plurality of the output links, or both, are arrangedin frames of a time division multiplexing protocol.
 5. The method ofclaim 1, wherein the defined connection is a point-to-point connection.6. The method of claim 1, wherein scheduling the idle data fortransmission over the at least one of the plurality of output links isfurther responsive to receiving, from another network device and fromoutside of the plurality of input streams, one or more parametersindicating that the input stream is empty.
 7. A network devicecomprising: memory; and processor circuitry operatively connected to thememory and configured to: receive a plurality of symbol blocks via aplurality of input streams, the plurality of symbol blocks to betransmitted within a predefined time period over a plurality of outputlinks comprised in a defined connection; serialize the plurality ofsymbol blocks received via the plurality of input streams into a servicestream, and in response, schedule transmission of each of the pluralityof symbol blocks on one of the plurality of output links, wherein toschedule the transmission the processor circuitry is configured todistribute the symbol blocks from the service stream to the plurality ofoutput links according to a mapping of symbol blocks to output links;responsive to an input stream of the plurality of input streams beingempty, schedule idle data for transmission over at least one of theplurality of output links such that the mapping of symbol blocks tooutput links is maintained; transmit over the defined connection via theplurality of output links according to the scheduling of the pluralityof symbol blocks and the idle data.
 8. The network device of claim 7,wherein to schedule the idle data for transmission the processorcircuitry is configured to schedule the idle data to fully utilizetransmission capacity of the plurality of output links that will not beconsumed by the transmitting of the plurality of symbol blocks.
 9. Thenetwork device of claim 7, wherein to schedule transmission of each ofthe plurality of symbol blocks the processor circuitry is configured toschedule transmission of at least one of the plurality of symbol blocksaccording to an instruction from a remote management node.
 10. Thenetwork device of claim 7, wherein the plurality of input streams, theplurality of the output links, or both, are arranged in frames of a timedivision multiplexing protocol.
 11. The network device of claim 7,wherein the defined connection is a point-to-point connection.
 12. Thenetwork device of claim 7, wherein to schedule the idle data fortransmission over the at least one of the plurality of output links, theprocessor circuitry is configured to be further responsive to receiving,from another network device and from outside of the plurality of inputstreams, one or more parameters indicating that the input stream isempty.
 13. A non-transitory computer readable medium storing a computerprogram product for controlling a programmable network device, thecomputer program product comprising software instructions that, when runon the programmable network device, cause the programmable networkdevice to: receive a plurality of symbol blocks via a plurality of inputstreams, the plurality of symbol blocks to be transmitted within apredefined time period over a plurality of output links comprised in adefined connection; serialize the plurality of symbol blocks receivedvia the plurality of input streams into a service stream, and inresponse, schedule transmission of each of the plurality of symbolblocks on one of the plurality of output links, the scheduling of thetransmission comprising distributing symbol blocks from the servicestream to the plurality of output links according to a mapping of symbolblocks to output links; responsive to an input stream of the pluralityof input streams being empty, schedule idle data for transmission overat least one of the plurality of output links such that the mapping ofsymbol blocks to output links is maintained; transmit over the definedconnection via the plurality of output links according to the schedulingof the plurality of symbol blocks and the idle data.